The study of soil is called pedology. The best pH of soil for crop cultivation is 5.5 to 6.8.

Timber line is an imaginary line in a mountain or higher areas of land that marks the level above which trees do not grow. The altitudinal limit of normal tree growth is about 3000 to 4000 m.

Raunkiaer classified the world's vegetation into the following four types. They are megatherms, mesotherms, microtherms and hekistotherms.

Sandy soil loses water at high rate, These characters along with other parameters such as p^H, mineral composition is also important.

Soil formation is initiated by the weathering process. Biological weathering takes place when organisms like bacteria, fungi, lichens & plants help in the breakdown of rocks through the production of acids & certain chemical substances.

A desert has little or no plant life without plants, there is no organic horizon in the soil leading to a low level of water retention that is unsuitable for plant growth.

Certain plants can also be used to remove cadmium from contaminated soil, this is known as phytoremediation.
Example: Eichhornia

The blue green light have short wavelength & penetrates into the water. Green algae is unable to use that component of light. Blue light can penetrate up to 500 ft depth therefore algae are unlikely to survive below that depth.

1. Eurythermal: Organisms which can tolerate a wide range of temperature fluctuations.
2. Stenohaline: Organisms which can withstand only small range of salinity.
3. These variations the organisms also grow in different environment.

Taxonomically different species occupying similar habitats (Niches) in different geographical regions are called Ecological equivalents.
E.g: Certain species of epiphytic orchids of Western Ghats of India differ from the epiphytic orchids of South America. But they are epiphytes.

The interaction of organisms with their environment results in the establishment of grouping of organisms
Levels of ecological hierarchy

1. It deals with the study of environment in relation to organisms.
2. It can be studied by considering individual organisms, population, community, biome or biosphere and their environment.

Aerosols with small particles is reflecting the solar radiation entering the atmosphere. This is known as Albedo effect.
Effects:
1. It reduces the temperature limits, photosynthesis & respiration.
2. The sulphur compounds are responsible for acid rain due to acidification of rain water and destroy the ozone.

The differences between habitat and niche are as follows.

S. No	Habitat	Niche
1	A specific physical space occupied by an organism (species).	A functional space occupied by an organism in the same eco-system
2	Same habitat may be shared by many organisms (species).	A single niche is occupied by a single species.
3	Habitat specificity is exhibited by organism.	Organisms may change their niche with time and season

1. In many species of fig trees, there is a one-to one relationship with the pollinator species of wasp. It means that a given fig species can be pollinated only by its 'partner' wasp species & no other species.
2. The female wasp uses the fruit not only as an oviposition (egg, laying) site but uses the developing seeds within the fruit for nourishing its larvae.
3. The wasp pollinates the fig inflorescence while searching for suitable egg-laying sites.
4. In return for the favour of pollination the fig offers the wasp, some of its developing seeds, as food for the developing wasp larvae.
5. The relationship that operates here is co-evolution.